Geology of the Falkland Islands

The geology of the Falkland Islands is described in several publications. The Falkland Islands are located on a projection of the Patagonian continental shelf. In ancient geological time this shelf was part of Gondwana, which around 400 million years ago broke from what is now Africa and drifted westwards relative to Africa. Studies of the seabed surrounding the islands indicated the possibility of oil. Intensive exploration began in 1996, although there had been some earlier seismic surveys in the region.

The geological history of the Falkland Islands began more than thousand million years ago (Mya), before they existed as separate islands. From its earliest history the Falklands Islands has been linked to South America. Evidence from xenoliths suggests that the lithosphere of Deseado Massif in southern Patagonia formed 2100 to 1000 Mya in the Paleo and Mesoproterozoic. Since these times the Falklands Islands and Deseado Massive have formed a single tectonic block. Like today both regions were next to each other during the Neoproterozoic when they formed part of the ancient supercontinent of Rodinia.

About 290 million years ago, in the Carboniferous period, an ice age engulfed the area as glaciers advanced from the polar region, eroding and transporting rocks. These rocks were deposited as extensive moraines and glacial till. When the glacial sediments were turned into stone they formed the rocks that now make up the Fitzroy Tillite Formation in the Falklands. Identical rocks are found in southern Africa.

The breakup of Gondwana in the Mesozoic Era led to the formation of a large number of minor crustal fragments, including the Falkland Islands. At first, the fragment containing the islands separated from the southeastern part of Africa on a section that would become Antarctica and later rotated by almost 180°. The interior of Gondwana was based on crystalline rocks more than a billion years old; in the Falklands today these are found in the Cape Meredith complex. Sand and mud filled and eventually covered the developing continental rifts. Later these sediments covering the rifts hardened into rock. These rock sequences from Gondwana's break-up can be identified in places as far apart as South Africa, western Antarctica and Brazil. In the Falkland Islands, these sequences are known as the West Falkland Group.

...
Wikipedia